Document Outline
- FEATURES
- GENERAL DESCRIPTION
- ORDERING INFORMATION
- QUICK REFERENCE DATA
- BLOCK DIAGRAM
- PINNING
- FUNCTIONAL DESCRIPTION
- RF amplifier
- Automatic laser power control circuit
- LIMITING VALUES
- QUALITY SPECIFICATION
- CHARACTERISTICS
- APPLICATION INFORMATION
- PACKAGE OUTLINE
- SOLDERING
- DEFINITIONS
- LIFE SUPPORT APPLICATIONS
DATA SHEET
Product specification
File under Integrated Circuits, IC01
1998 Oct 30
INTEGRATED CIRCUITS
TZA1025
Data amplifier and laser supply
circuit for CD audio and video
optical systems (ADALASLC)
1998 Oct 30
2
Philips Semiconductors
Product specification
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASLC)
TZA1025
FEATURES
Supports a wide range of voltage output mechanisms
RF amplifier designed for audio and video applications
with 1
data rate
Programmable RF gain for CD-Audio/Video (CD-A/V)
and CD-Read/Write (CD-R/W) discs
Equalizer for optimal performance
Fully Automatic Laser Power Control (ALPC) including
stabilization plus a separate laser supply voltage for
power efficiency
Adjustable current range of ALPC output
Automatic N- or P-substrate monitor diode selection
Adjustable laser bandwidth and laser switch-on current
slope using external capacitor
Protection circuit to prevent laser damage due to laser
supply voltage dip
Optimized interconnection between data amplifier and
Philips' digital signal processor CD10LC (SAA7325)
Wide supply voltage range
Power-down switch to reduce power consumption
during standby
Low power consumption.
GENERAL DESCRIPTION
The TZA1025 is a data amplifier and laser supply circuit for
voltage output mechanisms found in a wide range of audio
and video CD systems. The device contains an RF
amplifier and an automatic laser power control circuit.
The preamplifier forms an interface for voltage output CD
mechanisms to the Philips' digital signal processor
CD10LC (SAA7325).
The RF bandwidth allows this device to be used in CD-A/V
applications with a data rate of n = 1 times speed. The RF
gain can be adapted for CD-A/V discs or CD-R/W discs by
means of the gain select signal.
The equalizer ensures an optimal performance.
The TZA1025 can be adapted to a wide range of voltage
output mechanisms by means of external resistors.
The ALPC circuit will maintain control over the laser diode
current. With an on-chip reference voltage generator, a
constant and stabilized output power is ensured
independent of ageing. The ALPC can accommodate
N- or P-substrate monitor diodes.
A separate supply voltage connection for the laser allows
the internal power dissipation to be reduced by connecting
a low voltage supply. The laser output current range can
be optimized to fit the requirements of the laser diode by
means of one external resistor. When a DC-to-DC
converter is used, in combination with the control loop of
the ALPC, the adjustable output current range provides
the possibility to compensate for the extra gain a DC-to-DC
converter introduces in the control loop.
ORDERING INFORMATION
TYPE
NUMBER
PACKAGE
NAME
DESCRIPTION
VERSION
TZA1025T
SO14
plastic small outline package; 14 leads; body width 3.9 mm
SOT108-1
1998 Oct 30
3
Philips Semiconductors
Product specification
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASLC)
TZA1025
QUICK REFERENCE DATA
BLOCK DIAGRAM
SYMBOL
PARAMETER
CONDITIONS
MIN.
TYP.
MAX.
UNIT
Supplies
V
DD
supply voltage
2.4
-
5.5
V
I
DD
supply current
-
3
-
mA
V
DD(L)
laser supply voltage
2.4
-
5.5
V
RF amplifier
t
d(f)(RF)
RF flatness delay
-
-
10
ns
Laser supply circuit
I
o(LASER)(max)
maximum laser output current
V
DD(L)
-
V
o(LASER)
= 0.55 V
80
-
-
mA
V
i(mon)
monitor input voltage
N-substrate monitor diode
-
0.150
-
V
P-substrate monitor diode
-
V
DD
-
0.150
-
V
Temperature range
T
amb
operating ambient temperature
0
-
70
C
Fig.1 Block diagram.
(1) Band gap reference voltage.
handbook, full pagewidth
MBK902
250
kHz
8
TZA1025
14
3
7
10
1
12
9
V/I
V/I
VDD(L)
VDD
GND
2
6
VGAP
MON
4
(1)
DIN
5
CDRW
11
VDD
13
LD
CFIL
PWRON
RGADJ
CMFB
RFFB
RFEQO
GND
1998 Oct 30
4
Philips Semiconductors
Product specification
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASLC)
TZA1025
PINNING
FUNCTIONAL DESCRIPTION
The TZA1025 consists of two sections, the RF amplifier
and the automatic laser power control circuit.
RF amplifier
The RF amplifier consists of a current input amplifier, an
equalizer/bandwidth section and a transimpedance output
amplifier with an external feedback resistor of 10 k
(fixed
value).
SYMBOL
PIN
DESCRIPTION
LD
1
current output to laser diode
V
DD(L)
2
laser supply voltage
CFIL
3
external filter capacitor
MON
4
laser monitor diode input
DIN
5
central diode input
GND
6
ground
PWRON
7
power-on select input
CMFB
8
common mode feedback voltage
input
RFFB
9
external RF feedback resistor
RFEQO
10
RF amplifier output
CDRW
11
gain select input for CD-A/V, CD-R/W
GND
12
ground
V
DD
13
supply voltage
RGADJ
14
external laser supply gain adjust
resistor
Fig.2 Pin configuration.
handbook, halfpage
MBK901
TZA1025
1
2
3
4
5
6
7
8
14
13
12
11
10
9
LD
VDD(L)
CFIL
MON
DIN
GND
PWRON
CMFB
RFFB
RFEQO
CDRW
GND
VDD
RGADJ
The gain of the RF amplifier can be adjusted by the
external input resistors. Fig.3 shows the simplified
schematic which can be used to determine the RF gain.
The signal is AC coupled to the RF amplifier. The formula
to determine the gain is shown below:
(1)
where:
G
RF
is the RF amplifier gain
n is the number of input resistors
Z
tr(RF)
is the transimpedance of the amplifier (
)
R2 is the value of the input resistors (
).
The gain can be increased by a factor of 4 by making
pin CDRW HIGH. The value of Z
tr(RF)
is 9.8 k
for CD-A/V
(CDRW = LOW) and 38 k
for CD-R/W (CDRW = HIGH).
An internal equalizer ensures an optimal performance.
The DC output level of the amplifier can be set by applying
a DC voltage on the common mode feedback pin CMFB.
Since the input signal is AC-coupled the RF output voltage
will swing (symmetrically) around this DC level.
The coupling of the TZA1025 to the signal processor
(SAA7325) can be either AC or DC. When an AC-coupling
is chosen (see Fig.6) the minimum supply voltage can be
applied. When a DC-coupling is chosen (see Fig.7) a
minimum supply voltage of 2.8 V is required.
G
RF
n
Z
tr RF
(
)
R2
------------------
=
Fig.3 Simplified schematic.
handbook, halfpage
CDRW
RFEQO
C2
10 k
Vin
R2(1)
R2(2)
R2(n)
Vin
Vin
MGL530
1998 Oct 30
5
Philips Semiconductors
Product specification
Data amplifier and laser supply circuit for CD
audio and video optical systems (ADALASLC)
TZA1025
Automatic laser power control circuit
The ALPC stabilises the laser output power thereby
reducing the effect of ageing of the laser.
The TZA1025 automatically detects when an
N- or P-substrate monitor diode is used and selects the
correct reference voltage. A simplified diagram for the use
of an N- or P-substrate monitor diode is given in Fig.4.
The gain of the loop can be controlled (reduced) by adding
an external resistor between pins RGADJ and GND.
The loop gain then becomes:
(2)
where:
G
loop
is the loop gain
G
ALPC
is the ALPC transfer (60 A/V)
G
lm
is the laser-to-monitor transfer (V/A)
G
con
is the extra gain introduced when a DC-to-DC
converter is used in the loop; G
con
= 1 when no
DC-to-DC converter is used
250 is a fixed internal resistor value (
)
R
RGADJ
is the value of the external resistor (
).
The minimum available output current is also reduced
when an external resistor is used. The formula to
determine the minimum available output current is shown
in equation (3).
(3)
G
loop
G
ALPC
G
lm
G
con
250
250
R
RGADJ
+
-------------------------------------
=
I
o
I
o(LASER)(max)
250
250
R
RGADJ
+
-------------------------------------
=
where:
I
o
is output current (mA)
I
o(LASER)(max)
is the maximum laser output current (mA)
250 is a fixed internal resistor value (
)
R
RGADJ
is the value of the external resistor (
).
The bandwidth of the loop is determined by the external
filter capacitor C
CFIL
and the loop gain. The formula to
determine the bandwidth is shown in equation (4).
(4)
where:
C
CFIL
is the value of the capacitor (F)
G
loop
is the loop gain.
The TZA1025 has a protection circuit to prevent laser
damage that can occur due to a dip of V
DD(L)
. When a dip
occurs the output transistor (see Fig.4) will go into
saturation making it unable to supply the required laser
current. Without the protection circuit the ALPC would still
try to supply the required laser current by charging the filter
capacitor C
CFIL
. After the dip a fully charged capacitor
would create a large output current during the few
milliseconds it needs to discharge the capacitor to a
normal level. The protection circuit monitors the output
transistor and switches off the ALPC when saturation
occurs by discharging the capacitor. The ALPC will
automatically restart within a few milliseconds after the dip
has passed.
-3dB
C
CFIL
16 10
6
G
loop
------------------------------------------
=
Fig.4 Automatic Laser Power Control (ALPC) loop.
a. N-substrate monitor diode.
b. P-substrate monitor diode.
handbook, full pagewidth
MGR519
DC-TO-DC
CONVERTER
CCFIL
CCFIL
VDD(L)
150 mV
DC-TO-DC
CONVERTER
VDD(L)
VDD
VDD
-
150 mV
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